An obsessive killer who stabbed a young couple to death outside a city centre Matalan text his dad "thanks for being a pathetic father, just killed two people" moments after the jealousy-fuelled murders.

Andrew Saunders, 21, repeatedly stabbed Zoe Morgan and Lee Simmons in a terrifying knife rampage outside the store on Queen Street in Cardiff city centre on September 28 last year.

Moments later he sent a message to his dad saying: “Thanks for being a pathetic, useless father.

“Just killed two people. Cheers.”

Saunders, who admitted murder last month, had become obsessed with 21-year-old Miss Morgan and sent her a message saying "you're a f***ing whore for getting with him" before launching the attack.

The killer had split with Miss Morgan months earlier and messaged her "this is so unfair so tell me where he lives and I’ll f***ing torch his house" after learning she had started dating 33-year-old co-worker Mr Simmons.

A sentencing hearing at Cardiff Crown Court heard he lay in wait for the pair to arrive at the store at around 5.50am and brandished an eight-inch knife from his backpack.

CCTV footage shown to the court showed him launch into a "frenzy", stabbing Mr Simmons repeatedly in his chest.

As Miss Morgan attempted to pull the killer away he told her "I'm coming for you next you b****" before chasing her to a nearby Boots and stabbing her in the throat with a second, 10-inch knife.

The couple's bodies were left lying on the street outside the store (Image: Wales News Service)

A large section of Cardiff city centre was closed off following the killings (Image: Wales News)

Just hours before the killings he searched "how to slice a neck" online as well as other terms such as "motivation for killing", "motivation for revenge" and "how to smoke a cigar".

Miss Morgan and Mr Simmons met at work in July 2016 and started dating a short time later.

News of their relationship sent Saunders into a spiral of fury as he searched terms online including "16 steps to kill someone and not get caught", "How long do murders get in prison?" and "How to get a gun illegally UK".

A week before the murders he searched murder methods, including "How to knife someone’s neck" and "How can a car be rigged to explode when started".

He also messaged Miss Morgan telling her he still loved her.

When arrested by police, Saunders said he wanted to know if the couple were both dead for "peace of mind".

Floral tributes were left by shocked shoppers (Image: PA)

The store was closed following the attack (Image: PA)

He told officers: "Sometimes, you just snap. I’m really sorry for what I did. I just lost control.

“Your head is a weird thing. Have you ever been involved with someone?

“Are they both dead? I just want to know for peace of mind.”

Defending, Winston Roddick told the court Saunders was badly affected by the death of his grandfather and had left suicide notes before the killings.

He said: "They paint a picture of his state of mind and the struggle he was having through life.

"His judgement was undoubtedly impaired by a combination of factors.

"He is genuinely remorseful for what he has done and more than once said he wishes to turn the clock back."